ABSTRACT
Drainage is widespread. The first drainage shown here is open channels. This was used anciently on marsh and fen (and raised bogs on them), and has newly spread, from raised to blanket bog. Blanket bog is in the least populated areas. After surface drainage comes,
Table 11.1 Loss of European mires (from Heathwaite, in Hughes and Heathwaite 1995)
Country Loss
The Netherlands and Poland All exploited Switzerland and Germany 500 ha remain Ireland 80 000 ha drained since 1946 Britain 90% loss of blanket bog
98% loss of raised bog: 445 ha remain
in agricultural areas, under-drainage; alluvial flood plains may be in this next stage, with under-drainage, carrying water from the slope above direct to the stream. If much water comes from the slope above, there may be a catchwater drain running along the outside of the wetland, receiving run-off and again taking it direct to the stream, removing this ‘wetland water’ from it. The river is embanked, removing that source of ‘wetland water’ from the wetland. Both processes alter the water quality in the wetland: POLLUTION. The river hydrological system is by now separated, decoupled as it is termed, from the flood plain. This disrupts hydrological cycling and the cleaning function of the wetland.
